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Environ Toxicol Chem. 2018 Mar;37(3):674-689. doi: 10.1002/etc.4049. Epub 2018 Feb 12.

Prospective aquatic risk assessment for chemical mixtures in agricultural landscapes.

Author information

Waterborne Environmental, Leesburg, Virginia, USA.
Environment Department, University of York, Heslington, York, United Kingdom.
Syngenta, Jealott's Hill, Bracknell, United Kingdom.
Bayer CropScience, Research Triangle Park, North Carolina, USA.
Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, United Kingdom.
National Institute for Public Health and the Environment (RIVM), Centre for Sustainability, Environment and Health, Bilthoven, The Netherlands.
Radboud University, Department of Environmental Science, Institute for Wetland and Water Research, Faculty of Science, Radboud University, Nijmegen, The Netherlands.
US Food and Drug Administration, Center for Veterinary Medicine, Rockville, Maryland.
Elanco Animal Health, Greenfield, Indiana, USA.
Centre for Agroecology, Water and Resilience, Coventry University, Coventry, West Midlands, UK.
BASF SE, Crop Protection-Ecotoxicology, Limburgerhof, Germany.


Environmental risk assessment of chemical mixtures is challenging because of the multitude of possible combinations that may occur. Aquatic risk from chemical mixtures in an agricultural landscape was evaluated prospectively in 2 exposure scenario case studies: at field scale for a program of 13 plant-protection products applied annually for 20 yr and at a watershed scale for a mixed land-use scenario over 30 yr with 12 plant-protection products and 2 veterinary pharmaceuticals used for beef cattle. Risk quotients were calculated from regulatory exposure models with typical real-world use patterns and regulatory acceptable concentrations for individual chemicals. The results could differentiate situations when there was concern associated with single chemicals from those when concern was associated with a mixture (based on concentration addition) with no single chemical triggering concern. Potential mixture risk was identified on 0.02 to 7.07% of the total days modeled, depending on the scenario, the taxa, and whether considering acute or chronic risk. Taxa at risk were influenced by receiving water body characteristics along with chemical use profiles and associated properties. The present study demonstrates that a scenario-based approach can be used to determine whether mixtures of chemicals pose risks over and above any identified using existing approaches for single chemicals, how often and to what magnitude, and ultimately which mixtures (and dominant chemicals) cause greatest concern. Environ Toxicol Chem 2018;37:674-689. © 2017 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.


Agriculture; Chemical mixture; Exposure scenario; Landscape; Risk assessment

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